Frequency dispersion in elastic property during the glass transition of dehydrated polyacrylamide gel

The elastic property evolution with increasing temperature of dehydrated polyacrylamide (PAAm) gel has been measured with a vibrometer at several frequencies. The elastic stiffness (Young's modulus) showed marked changes (significant decrease in the real part and a clear peak in the imaginary part) around a characteristic temperature, which shifted toward the higher region with increasing applied frequency, similar to the features observed during the glass transition of noncrystalline polymers. The activation energy of the elastic stiffness relaxation was also calculated with the peak temperature of the imaginary part and the applied frequency. The activation energy value of the dehydrated PAAm gel was in the range usually observed for noncrystalline polymers, based on which dehydrated PAAm gel has been confirmed to have the properties usual for noncrystalline polymer glass from an elastic point of view.